Electromagnet system for lifting and lowering a rod
structure in a tubular housing



May 25, 1965 G. JAHN 3,185,909

ELECTROMAGNE'I' SYSTEM FOR LIFTING AND LOWERING A ROD STRUCTURE IN ATUBULAR HOUSING 2 Sheets-Sheet 1 Filed May 51, 1962 May 25, 1965 G. JAHN3,185,909

ELECTHOMAGNET SYSTEM FOR LIFTING AND LOWERING A ROD STRUCTURE IN ATUBULAR HOUSING Filed May 51, 1962 2 Sheets-Sheet 2 FIG. 2

FIG. 3

United States Patent 0 3,185,969 ELECTROMAGNET SYSTEM FGR LIFTING ANDLGWERING A R61) STRUCTURE IN A TUBULAR HOUSENG Giinther Jahn, Erlangen,Germany, assignor to Siemens- Schuckertwerke Aktiengesellschaft,Berlin-Siemeusstadt, Germany, a German corporation Filed May 31, 1962,Ser. No. 199,095 Claims priority, application Germany, June 6, 1961,

2 Claims. ci. sis-13s My invention relates to electromagnetic apparatusfor lifting and lowering a rod-shaped structure in a tubular housing bymagnetic force acting from the outside through the housing wall. Suchapparatus are applicable particularly in nuclear reactor plants forshifting the regulating and shut-oft rods.

In a more particular aspect my invention relates to improvements ofelectromagnetic apparatus according to the copending application of F.Schreiber and H. Kumpf,

gizing the excitation windings in a progressing sequence 9 the rodstructure is lifted or lowered, depending upon the direction of thesequence. Each two adjacent excitation coils are so wound orelectrically interconnected that the resulting magnetic fluxes in thepole common to the two windings have the same direction and thus augmenteach other. The uppermost and lowermost magnet poles, however, are eachtraversed only by the magnetic flux induced by a single excitation coil.Consequently, the proportion of stray flux passing through the housingwithout being active upon the rod structure is greater at the uppermostpole and the lowermost pole than at any of the intermediate poles. Thismanifests itself unfavorably when during the progressive excitation ofthe coils the excitation is switched from theuppermost coil to thelowermost coil. Then there occurs an interval of time in which thelifting force temporarily drops to a lower value than ob tained duringthe preceding period of time in which the other coils of the group ofelectromagnets are sequentially energized. As a result, the liftingforce may be temporarily insufficient or unreliable for producing thedesired continuity of lifting operation, or it is necessary tooverdimension the electromagnets in order to make certain that thelifting power always stays above the required minimum value.

It is an object of my invention to minimize or obviate thesedisadvantages.

To this end, and in accordance with a feature of my invention I providethe group of magnets, axially aligned along the tubular housing in whichthe teethed rod structure is displaceable, with additional magnetizablemeans which are joined with the lowermost pole of the group ofelectromagnets, the additional magnetizing means being poled influx-augmenting sense relative to the lowermost pole and activesimultaneously with the uppermost electromagnet of the group.

According to another more specific feature of my invention, theadditional magnetizing means joined with the lowermost pole of thesequentially energized electromagnets of the group consists likewise ofan electromagnet except that its excitation coil is switched onsimultaneously with the excitation coil located between the twouppermost magnet poles of the group.

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The invention will be further described with reference to an embodimentillustrated by way of example on the accompanying drawings in which:

FIG. 1 is a partly sectional view of an electromagnetic apparatus forlifting and lowering a moderator rod or similar structure in a nuclearreactor.

FIG. 2 is the circuit diagram of appertaining sequencing means.

FIG. 3 shows a portion of a modified circuit diagram also applicablewith such apparatus.

As shown in FIG. 1, an enclosure 3, such as the tank of a nuclearreactor, is flanged together with a tubular housing 2 consisting of apressure-resistant tube of magnetizable material. Mounted on thepressure tube 2 is a group of electromagnets comprising for example,eight excitation coils I to 1 with appertaining magnet poles 3, 4, 5,and ring-shaped yoke pieces 6 of magnetizable material. Attached to thelowermost electromagnet with coil I of the above-mentioned group isanother electromagnet whose excitation coil is denoted by I The coil Iis electrically connected in parallel to the uppermost coil 1 of thesequentially energized electromagnets so that coils I and I are alwaysswitched on and off simultaneously, as will be further explained withreference to FIGS. 2 and 3.

The structure 13 to be displaced is located in the interior of thetubular housing tube. The structure 13 consists of a tubular rod formedessentially of magnetizable material and provided with rings 14 thatconstitute rack teeth and are uniformly distributed over the entirelifting stroke of the rod structure. The number of tooth rings 14,counted along the axial extent of the nine poles 3, 4, 5 that form partof the sequentially energized electromagnet with coils I to I differsfrom the number of magnet poles in accordance with a given Vernier ratioas explained in the above-mentioned copending application, Serial No.127,374. Thus, in the embodiment illustrated in FIG. 1, ten teeth 14occupy the same axial length as the above-mentioned nine poles. As aresult, the rod structure 13 is gradually and uniformly lifted orlowered when the coils I and I are successively energized in a cyclicalsequence.

The inner surface of the tubular rod structure 13 is coated withneutron-absorbing substance 15 such as boron, for example.

For increasing the pulling force, several adjacent excitation coils, forexample four coils, are preferably switched on simultaneously. Forprogressively displacing the rod structure, one coil at a time is addedto the energized subgroup and the previously first-energized coil of thesubgroup is simultaneously switched Off. Also for increasing the pullingforce, one or more additional groups of electromagnets can be added,each comprising eight individual electromagnets (or generally the samenumber of electromagnets as the first-mentioned group), the excitationcoils of the individual groups being switched on and off in the samesequence as the corresponding coils of the first group. In these casestoo, it is advisable to provide the additional magnet means, for examplethe additional coil 1 When the groups of electromagnets are spaciallyseparate from each other, each group is preferably provided with anadditional electromagnet I An energizing circuit for coils I to I andfor the additional coil I is schematically illustrated in FIG. 2together with a sequence controller of the cam-type. A reversibleelectric motor 29 drives a cam shaft 21 with a separate cam switch 22for each of the respective excitation coils in the illustratedembodiment. The cams are so set that four coils of the group aresimultaneously energized, except that the additional I is alwaysswitched on and off simultaneously with the coil 1 The condition shownin FIG. 2 relates to operation of the motor 20 for lifting the rodstructure and represents a moment when coils L, to 1 are switched ontogether with the additional I This moment is just prior to the transferof excitation to coil I That is, at the next switching stage the coil1;, is switched off and the coil I is switched on. At that moment theadditional coil I is still energized, thus augmenting the magnetic fluxin the lowermost pole 3 then jointly traversed by flux from coils I andI At the next stage the coil I is switched off and the coil 1 isswitched on, and so forth.

A simultaneous excitation of coils I and I can also be effected by meansof a single control contact and a direct parallel connection of the twocoils as shown in FIG. 3, the rest of the circuit diagram being inaccordance with FIG. 2.

It will be obvious to those skilled in the art that my invention isapplicable in various modifications and together with such varieties ofmagnetic-jack apparatus as described, for example, in theabove-mentioned copending application, Serial No. 127,374 or in thecopending application, Serial No. 199,004 of Franz Schreiber filedconjointly with the present application and based upon the same Germanpriority of June 6, 1961. My invention can therefore be givenembodiments other than particularly illustrated and described herein,without departing from the essential features of my invention and withinthe scope of the claims annexed hereto.

I claim:

1. Electromagnetic apparatus for lifting and lowering a rod structurewithin an enclosure by magnetic force applied from the outside,comprising a tubular housing and a rod structure longitudinallydisplaceable therein in lifting and lowering directions, a multiplicityof electromagnets axially aligned along said housing at the outsidethereof and having uniformly spaced magnet poles, said rod structurehaving magnetizable teeth forming armatures for said respective magnets,the number of said teeth along the length of said multiplicity ofaligned magnets differing from the number of said poles in accordancewith a vernier ratio, energizing electric circuit means connected withsaid electromagnets and having sequence switch means for progressivelyenergizing a given subgroup of cyclically adjacent ones of saidelectromagnets at a time to selectively cause displacement of said rodstructure in one of said respective directions through successive unitdistances corresponding to the spacing between two adjacent poles aseach new lead magnet of said progressively energized subgroup isenergized in direct sequence, and additional magnetizing means joinedwith the lowermost one of said poles of said group and poled influx-augmenting sense relative to said lowermost pole for magneticallyincreasing the displacing force exerted by said lowermost pole on saidrod structure, said additional magnetizing means being activesimultaneously with the uppermost one of said electromagnets of saidmultiplicity of electromagnets.

2. Electromagnetic apparatus for lifting and lowering a rod structurewithin an enclosure by magnetic force applied from the outside,comprising a tubular housing and a rod structure longitudinallydisplaceable therein in lifting and lowering directions, a multiplicityof electromagnets axially aligned along said housing at the outsidethereof and having uniformly spaced magnet poles, said rod structurehaving magnetizable teeth forming armatures for said respective magnets,the number of said teeth along the length of said multiplicity ofaligned magnets differing from the number of said poles in accordancewith a Vernier ratio, energizing electric circuit means connected withsaid electromagnets and having sequencing switch means for progressivelyenergizing a given subgroup of cyclically adjacent ones of saidelectromagnets at a time to selectively cause displacement of said rodstructure in one of said directions through successive unit distancescorresponding to the spacing between two adjacent poles as each new leadmagnet of said progressively energized subgroup is energized in directsequence, and an additional electromagnet joined with the lowermost oneof said poles of said group for augmenting the magnetic flux in saidlowermost pole for magnetically increasing the displacing force exertedby said lowermost pole on said rod structure, said additionalelectromagnet and the uppermost one of said multiplicity ofelectromagnets being in jointly controlled connection with said switchmeans so as to be energized simultaneously.

References tilted by the Examiner UNITED STATES PATENTS 668,978 2/01Carlson 310-14 X 1,132,445 3/15 Conrad 31014 1,817,638 8/31 Morris310-14 X 2,752,546 6/56 Frisch 310-14 X MILTON O. HIRSHFIELD, PrimaryExaminer.

DAVID X. SLINEY, Examiner,

1. ELECTROMAGNETIC APPARATUS FOR LIFTING AND LOWERING A ROD STRUCTUREWITHIN AN ENCLOSURE BY MAGNETIC FORCE APPLIED FROM THE OUTSIDE,COMPRISING A TUBULAR HOUSING AND A ROD STRUCTURE LONGITUDINALLYDISPLACEABLE THEREIN IN LIFTING AND LOWERING DIRECTIONS, A MULTIPLICITYOF ELECTROMAGNETS AXIALLY ALINED ALONG SAID HOUSING AT THE OUTSIDETHEREOF AND HAVING UNIFORMLY SPACED MAGNET POLES, SAID ROD STRUCTUREHAVING MAGNETIZABLE TEETH FORMING ARMATURES FOR SAID RESPECTIVE MAGNETS,THE NUMBER OF SAID TEETH ALONG THE LENGTH OF SAID MULTIPLICITY OFALIGNED MAGNETS DIFFERING FROM THE NUMBER OF SAID POLES IN ACCORDANCEWITH A VERNIER RATIO, ENERGIZING ELECTRIC CIRCUIT MEANS CONNECTED WITHSAID ELECTROMAGNETS AND HAVING SEQUENCE SWITCH MEANS FOR PROGRESSIVELYENERGIZING A GIVEN SUBGROUP OF CYCLICALLY ADJACENT ONES OF SAIDELECTROMAGNETS AT A TIME TO SELECTIVELY CAUSE DISPLACEMENT OF SAID RODSTRUCTURE IN ONE OF SAID RESPECTIVE DIRECTIONS THROUGH SUCCESSIVE UNITDISTANCES CORRESPONDING TO THE SPACING BETWEEN TWO ADJACENT POLES ASEACH NEW LEAD MAGNET OF SAID PROGRESSIVELY ENERGIZED SUBGROUP ISENERGIZED IN DIRECT SEQUENCE, AND ADDITIONAL MAGNETIZING MEANS JOINEDWITH THE LOWERMOST ONE OF SAID POLES OF SAID GROUP AND POLED INFLUX-AUGMENTING SENSE RELATIVE TO SAID LOWERMOST POLE FOR MAGNETICALLYINCREASING THE DISPLACING FORCE EXERTED BY SAID LOWERMOST POLE ON SAIDROD STRUCTURE, SAID ADDITIONAL MAGNETIZING MEANS BEING ACTIVESIMULTANEOUSLY WITH THE UPPERMOST ONE OF SAID ELECTROMAGNETS OF SAIDMULTIPLICITY OF ELECTROMGNETS.